The present invention relates generally to apparatus and methods for treating vascular conditions, and more specifically, to a balloon having a non-uniform configuration that improves the folding capability of the balloon after it is deflated.
Atherosclerosis and other occlusive diseases are prevalent among a significant portion of the population. In such diseases, atherosclerotic plaque forms within the walls of the vessel and blocks or restricts blood flow through the vessel. Atherosclerosis commonly affects the coronary arteries, the aorta, the iliofemoral arteries and the carotid arteries. Several serious conditions may result from the restricted blood flow, such as ischemic events.
Various procedures are known for treating stenoses in the arterial vasculature, such as balloon angioplasty. During a balloon angioplasty procedure, a catheter having a deflated balloon attached thereto is inserted into a patient's vessel. In some cases, it is desirable to introduce the balloon in a configuration whereby the balloon is twisted or folded upon itself in order to reduce the radial profile of the balloon during delivery. Once positioned across a constricting lesion, the balloon then is inflated to widen the lumen to partially or fully restore patency to the vessel. After satisfactory widening of the stenosis has been achieved, the balloon is deflated. The catheter then is retracted and removed from the patient's vessel with the balloon in the deflated state.
One problem that exists with conventional angioplasty balloons is that they may not collapse reliably after deflation. For example, after the balloon is expanded to engage the vessel wall and then deflated, the balloon may obtain a flattened configuration, e.g., having two opposing regions that extend radially outward. In those cases, it may be difficult to withdraw the balloon from the patient's vessel. If an introducer sheath is used, the balloon may become caught within the sheath upon retraction and removal.
At least one previously-known device has attempted to reduce the profile of a balloon in the deflated state by providing a non-uniform balloon wall thickness around the balloon circumference, thereby forming a deflated wing when the balloon is deflated. In particular, U.S. Pat. No. 6,544,224 to Steese-Bradley (hereinafter “the '224 patent”) discloses a balloon comprising a lobular outer surface after formation in a balloon mold. The balloon disclosed in the '224 patent is formed by providing a cylindrical balloon preform, and blow-molding the balloon preform within a mold having lobular or concave-shaped interior surfaces. Therefore, after it is formed, the balloon assumes a lobular-shaped outer surface, and has a non-uniform wall thickness about a portion of its circumference. The molded, non-uniform balloon of the '224 patent therefore comprises a substantially different shape compared to the uniform, cylindrical balloon preform. Moreover, the formation of the non-uniform wall thickness of the balloon of the '224 patent is based upon the provision of the non-cylindrical interior surface of the balloon mold.
In view of the foregoing, there is a need for a balloon that achieves a sufficiently collapsed radial profile after deflation in order to reduce the likelihood that the balloon will become caught upon removal from the patient's vessel.